Diltiazem does not always increase blood cyclosporin concentration

Area of Science:

• Pharmacology
• Transplant Medicine
• Drug Interactions

Background:

• Cyclosporine (CsA) is a vital immunosuppressant post-lung transplant.
• Drug interactions can significantly alter CsA efficacy and toxicity.
• Diltiazem (DTZ) is often used as a CsA-sparing agent, but its effectiveness can vary.

Purpose of the Study:

• To investigate the pharmacokinetic interaction between CsA, DTZ, and itraconazole (ICZ) in a single lung transplant patient.
• To evaluate the impact of co-prescribing DTZ or ICZ on CsA concentrations.

Main Methods:

• Case study of a single lung transplant patient.
• Monitoring of CsA area under the curve (AUC) estimations.
• Co-prescription of CsA with either DTZ or ICZ.

Main Results:

• Co-prescription of ICZ with CsA led to a significant increase in CsA AUC (5836 µg·l⁻¹·h vs. 8159 µg·l⁻¹·h).
• Co-prescription of DTZ with CsA did not increase CsA AUC (5836 µg·l⁻¹·h vs. 5069 µg·l⁻¹·h).

Conclusions:

• Itraconazole significantly elevates cyclosporine levels.
• Diltiazem did not increase cyclosporine concentrations in this patient, challenging its consistent role as a CsA-sparing agent.
• Clinical monitoring is crucial when co-prescribing these drugs, especially diltiazem with cyclosporine.